To date, there has been no practical way to measure, in near real time, the gross resistance and reactance of VLF, very low frequency and LF, low frequency, transmitting antennas while the antennas were on the air transmitting message traffic. These parameters could be measured only when the antenna was broadcasting a single frequency (CW), signal which contains no information. Therefore the transmitter effectively had to be taken out of service to make measurements of the resistance and reactance. Due to the operational requirement that these antennas need be on the air continuously for weeks at a time, taking them off the air to make these measurements only could be accomplished once or twice per month.
As a consequence, it could not be known with certainty if a particularly antenna transmitting system were operating properly in the interim so that reliable communications could be compromised without any indication of malfunction. The possibility of an undetected malfunction could have a eroding effect regarding the confidence of those depending on the reliability of the system as well limiting the system when compared to the intended capabilities of the system. The only capability that is currently available at the VLF and LF sites is measurement of the magnitude of the voltage and current at the transmitter output. No information on phase angle can currently be obtained and consequently the circuit parameters of the antenna and the associated tuning system resistance, Rg, capacitance, Cg and inductance, Lg are not measurable in near real time using contemporary measurement systems.
Thus, a continuing need exists in the state of the art for a system which provides for operational parameter measurements which could be made as frequently as one every second without taking an antenna out of service and, in addition, the system should have the capability for providing a PC, personal computer, based antenna voltage and current monitor system that allows remote monitoring via ordinary phone lines of the antenna parameters at any of the sites of remote antenna systems throughout the world.